Lab Update 24 – Laboratory Diagnosis and Monitoring of Schistosomiasis in South Africa

June 2021
Dr Mark da Silva & Dr Pieter Ekermans
Ampath | ampath.co.za

Epidemiology

Schistosomiasis transmission occurs with exposure to warm, slow-moving fresh water, often during:

• Swimming
• Fishing
• Washing clothes

The disease requires an aquatic intermediate host:

• Schistosoma haematobium: Bulinus snail species
• Schistosoma mansoni: Biomphalaria snail species

Endemic areas in South Africa:

• Limpopo
• Mpumalanga
• Northern and eastern Gauteng
• Coastal and lower-altitude regions of KwaZulu-Natal
• Extends to the Eastern Cape (as far south as Gqeberha/Port Elizabeth)

Suggested Diagnostic Approach

1. Asymptomatic Patients

Travellers and migrants:

• Initial screening: Serology (schistosoma-specific IgM, IgG, and IgE)
• If positive: Follow up with microscopy

Patients from endemic areas:

• Initial test: Antigen testing

2. Symptomatic Patients

Early infection (<3 months post-exposure):

• Initial serology, microscopy, and antigen testing may be negative
• If suspicion remains high: Consider PCR on blood, faeces, or urine

General symptomatic presentation:

• Initial screening: Serology (IgM, IgG, IgE)
• If positive: Follow up with microscopy
• May include: Antigen testing or PCR on blood, faeces, or urine

3. Suspected Ectopic Schistosomiasis

• Clinical assessment and radiology
• Microscopy of specimens (e.g. bronchial washing)
• Histological examination

4. Suspected Neuroschistosomiasis

• Clinical and radiological findings, preferably with extraneural disease evidence
• OR
  • CNS lesion histology
  • Serology (IgM, IgG, IgE)
  • PCR on CSF

5. Suspected Glomerular Disease

• Clinical evaluation
• Serology (IgM, IgG, IgE)
• Antigen testing
• Rectal submucosa biopsy
• Renal biopsy

Diagnostic Methods Overview

Microscopy

• Multiple samples (stool or urine) may be required
• Best urine collection time: Between 10 a.m. and 2 p.m.
• If infection is light or egg excretion is intermittent: Consider rectal snip

Antigen Testing

• CAA (circulating anodic antigen): Detected in serum; detects all schistosome species
• CCA (circulating cathodic antigen): Detected in urine; especially useful for S. mansoni
• Use midstream urine sample, refrigerate post-collection

Serology

• Detects schistosoma-specific IgM, IgG, and IgE
• Useful for initial diagnosis
• Antibody response may vary
• Note:
  • Non-human schistosomes may cause cross-reactions
  • Do not use for treatment follow-up

Haematology, Chemistry, and Other Investigations

Full Blood Count

• Eosinophilia: Early marker of infection
• Anaemia: Often hypochromic, microcytic
• Thrombocytopenia

Iron Studies

Blood Cultures

• Chronic schistosomiasis may cause prolonged Salmonella bacteraemia

Differential Diagnosis

• Always consider malaria in acute febrile illness

Further Investigations in Chronic Schistosomiasis

• Liver function tests
• Urea, creatinine, and electrolytes
• Urine culture
• HIV testing
• Hepatitis B and C serology
• Faecal occult blood and calprotectin
• Radiological imaging

Follow-Up Recommendations

Microscopy

• 6–8 weeks post-treatment:
  • Examine urine and stool for eggs
  • If still positive, repeat praziquantel treatment
• Continue to monitor for up to 6 months post-therapy

Antigen Testing

• Clearance may occur within days to weeks after successful treatment

Repeat parasitological studies if:

• Eosinophilia persists
• Haematuria recurs
• Symptoms return

📌 References available upon request.
📌 For further guidance, contact your local Ampath pathologist.